2010/11 Regulations of the UEFA Champions League http://www.uefa.com/MultimediaFiles/Download/Regulations/competitions/Regulations/01/48/42/49/1484249_DOWNLOAD.pdf "... Quarter-finals 7.11 The eight winners of the round of 16 contest the quarter-finals. The quarter- final pairings are determined by means of a draw. The quarter-finals are played under the knockout system, on a home-and-away basis (two legs). The team which scores the greater aggregate of goals in the two matches qualifies for the semi-finals. Otherwise, the stipulations of Article 8 apply. ...."